It is conventionally known that in a permanent magnet embedded brushless motor (IPM motor) configured such that permanent magnets are inserted into slots of a rotor, in order to achieve a higher output and a higher efficiency of the motor, an inner wall surface of a portion of the slot is formed not to contact the permanent magnet, and an iron plate portion between the inner wall surface of the portion of the slot and an outer edge of the rotor which is located radially outward relative to the inner wall surface is formed as a flux barrier portion for reducing a leakage of magnetic flux generated in the permanent magnet. By making the flux barrier portion thus formed as thin as possible, the higher output and the higher efficiency of the motor are achieved.
With the higher output and the higher-speed rotation of the motor, a centrifugal force exerted on the permanent magnet embedded into the slot and a portion of the rotor which is located radially outward relative to the permanent magnet increases. Because of this, if the flux barrier portion is thinned, it may be broken (fractured), so that the permanent magnet and the portion of the rotor which is located radially outward relative to the permanent magnet may fly off. To avoid this, there have been conventionally provided approaches for optimizing a shape of the flux barrier portion to enhance a strength of the flux barrier portion while reducing a leakage of the magnetic flux generated in the permanent magnet (see, e.g., Patent Literatures 1, 2).    Patent Literature 1: Japanese Laid-Open Patent Application Publication No. 2001-16809    Patent Literature 2: Japanese Laid-Open Patent Application Publication No. 2010-88219
However, in the conventional configurations including those disclosed in Patent Literatures 1 and 2, a problem that the flux barrier portion may be broken, occurs, if an attempt is made to rotate the rotor at a higher speed (e.g., a rotational speed which is equal to or greater than 100000 revolutions/minute (rpm)). To prevent the flux barrier portion from being broken, it is considered that the flux barrier portion is made thicker to ensure its strength, or the permanent magnet is reduced in size so that the centrifugal force exerted on the permanent magnet is reduced and thereby a force exerted on the portion of the rotor which is located outward relative to the permanent magnet is reduced. However, such an approach results in a low output and a low efficiency of the motor. Therefore, it is impossible to attain a higher-speed rotation of the motor while reducing a size of the motor.
In particular, it is demanded that a smaller size and a higher output of a fan driving motor applied to a suction fan of a vacuum cleaner can be attained, in order to attain a smaller size and a higher output of the vacuum cleaner. In a conventional fan driving motor, its regular revolutions are typically equal to or less than about 20000 rpm, and regular revolutions of a motor rotating at a high speed are about 40000 to 50000 rpm at most. Thus, a fan driving motor which is able to attain regular revolutions which are more than about 40000 to 50000 rpm has not been put into practice yet.
The present invention is directed to solving the above stated problems associated with the prior arts, and an object is to provide a rotator of a motor which is able to attain a high-speed rotation by appropriately dispersing a stress exerted on a flux barrier portion while reducing a leakage of magnetic flux, and a fan driving motor including the rotator.